Yb Impurity Research Articles

Characteristics of the incorporation of Yb defect states in CuO:ZnO nanocomposite

Exploring magnetic order in nonferromagnetic substances, such as CuO:ZnO, becomes especially attractive when introducing defect states through nonmagnetic ion doping. In this study, we delved into the impact of Yb doping on the structural, morphological, optical, and magnetic properties of CuO:ZnO. The Yb doped CuO:ZnO was prepared with different Yb concentrations (x = 0.00–20 %) via the temperature-assisted co-precipitation method. X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, and vibrating sample magnetometer (VSM) were used to investigate the structural, morphological, optical, and magnetic properties of Yb doped CuO:ZnO nanocomposites.The incorporation of Yb in CuO:ZnO nanocomposites leads to a notable shift of the characteristic XRD peaks of CuO and ZnO to lower angles, accompanied by an increase in the lattice parameters. UV–visible absorption spectroscopy shows an overall decrease in the optical band gap energy of ZnO as the Yb defect level increases. FE-SEM studies revealed the transformation of spherical structures into agglomerated non-spherical structures upon the introduction of Yb ions into CuO:ZnO nanocomposites. According to XPS data, the predominant valences of Yb-doped CuO:ZnO nanocomposites are Zn2+, Cu2+, and Yb3+. One noteworthy observation from the XPS results is that, in comparison to the intensity of OL or Oad peaks, the intensity of OV (Oxygen vacancy) defect peak increases when the Yb impurity concentration increases. Magnetic measurements demonstrated a diamagnetic order in pure ZnO, which converts to a ferromagnetic order with the incorporation of Yb defect states. The ferromagnetic properties of the Yb-doped CuO:ZnO nanocomposite can be ascribed to the exchange interaction of Yb3+ ions with defect states (Oxygen Vacancy) in ZnO and CuO.

Intrinsic electronic excitations and impurity luminescent centres in NaMgF3 and MgF2 doped with Yb2+

The relaxation pathways of states in the energy region of the fundamental absorption of NaMgF3:Yb2+ and MgF2:Yb2+ are investigated using time-resolved vacuum ultraviolet spectroscopy. For NaMgF3:Yb2+, excitation into intrinsic free exciton states or above the band gap results in emission features associated with self-trapped excitons and impurity-trapped excitons. Excitation into host-related states of MgF2:Yb2+ similarly exhibits self-trapped exciton emission as well as emission from Yb2+ 4f135d states. The excitation features related to Yb2+ 4f14→4f135d transitions are interpreted using semi-empirical crystal field models. For both materials, the interplay between intrinsic distortions and Yb impurity centres, as the excitation wavelength and sample temperature are varied, is presented and analysed.

Spectral Comparison of Neutron-Irradiated Natural and Enriched Ytterbium Targets for Lu-177 Production

Beta-emitting radioisotope 177 Lu has been suggested for radioimmunotherapy, peptide receptor radionuclide therapy, or another radionuclide therapy due to its excellent properties for destroying cancer cells. In this experimental investigation, natural ytterbium ( nat Yb) and enriched 176 Yb targets were irradiated with thermal neutrons at 1.2×10 14 cm -2 s -1 neutron flux for 95 hours. Using a high-purity germanium (HPGe) detector-based spectroscopy system, the post-irradiated targets were measured and the produced radioisotopes were identified according to their gamma ray emissions. Experimental results indicated that several radioisotopes such as 169 Yb and 175 Yb dominate the post-irradiated nat Yb target, though a relatively weak intensity of 177 Lu was also recorded. In contrast, 177 Lu radioisotope dominates the gamma rays observed in the post-irradiated enriched 176 Yb target following elution with HNO 3 solution. For the first time, evidence is found of 175 Yb impurity in the post-neutron-irradiated enriched 176 Yb 2 O 3 target as a result of 176 Yb(n,2n) 175 Yb nuclear reaction. This work recommends future 177 Lu radioisotope production using enriched 176 Yb 2 O 3 target.

Yb-doping effect on structure and lattice dynamics of Gd2O3

We report the results of a study that examines the effects of trivalent Yb impurities occupying different sites in cubic Gd2O3 on the latter’s structure and vibrational spectrum. The shell model is employed to compute relaxed structures and phonon symmetrized local densities of states. The lattice structure and dynamics of Yb-doped Gd2O3 are calculated using a cluster approach. The frequencies of localized vibrations caused by Yb ions are also determined. The results of lattice-dynamical calculations are compared with experimental data in literature.

Simulation of static and dynamic lattice properties of Yb-doped gadolinium oxide

Abstract The results of studying the effect of Yb ions on the lattice structure and the vibrational spectrum of cubic Gd2O3 are presented. The study was performed on the basis of modeling using a shell model. The calculations of equilibrium structures and phonon local symmetrized densities of states were carried out. The frequencies of localized vibrations of A- and B-symmetries induced by Yb impurity which occupies a position with the C2 site symmetry are also calculated. The results of the calculations are compared with the experimental data.

Electron traps in Gd3Ga3Al2O12:Ce garnets doped with rare-earth ions

The curves of thermally stimulated luminescence of Gd3Ga3Al2O12:Ce3+ ceramics (a nominally pure sample and samples doped with rare-earth ions) are measured in the temperature range of 80–550 K. The depth and the frequency factor of electron traps established by Eu and Yb impurities are determined. An energy-level diagram of rare-earth ions in the bandgap of Gd3Ga3Al2O12 is presented.

Optical properties of ZnSe(Te) with ytterbium impurity.

We report the results on infrared transmission measurements of non-doped and tellurium-doped crystals of zinc selenide grown from the melt. It was found that non-doped samples feature high transmission (50%-60%) for the wavelengths of 1-22μm. The efficient scintillating crystals of ZnSe(Te) are almost opaque for λ>7 μm. Doping these samples with ytterbium from the gas phase does not achieve any significant transmission increase for non-doped ZnSe samples in the spectral range of 1-22μm. However, it considerably increases (up to 50%) transmission for doped ZnSe(Te) at the wavelengths λ>10 μm. These optical peculiarities were analyzed taking into account restructurization of point defect ensembles created by Te and Yb impurities.

Influence of the ytterbium doping technique on the luminescent properties of ZnSe single crystals

Abstract Luminescent properties of the ytterbium doped zinc selenide crystals with 0.00–8.00 at % concentrations of the Yb impurity within the temperature interval from 6 K to 300 K were studied. Ytterbium doping was performed within three technological processes: during the growth by chemical vapor transport method and by thermal diffusion from the Bi+Yb or Zn+Yb melt. The influence of ytterbium impurity concentration on spectral position and intensity of the various photoluminescent bands in ZnSe emission spectra in visible and infrared range is analyzed. A tendency of ytterbium ions to form associates with background defects was demonstrated. A strong dependence between ytterbium influence on the zinc selenide emission spectra and concentration of selenium vacancies was shown.

Purification of ZnSe crystals from electrically active background impurities by ytterbium doping

Hall coefficient, electrical conductivity, and electron mobility are investigated for n-ZnSe:Yb single crystals with high concentration of electrically active background impurities ((cm) in the temperature range from 4.2 to 300 K. It is found that increasing concentration of Yb impurity in Zn + Yb melt from 0.03 to 4.00 at.% decreases the concentration of shallow and deep donors, as well as the concentration of compensating acceptors by nearly 2 orders of magnitude. A quantitative manifestation of purification of the ZnSe:Yb samples from non-controlled background electrically active impurities and influence of this effect on changes in impurity band parameters and the temperature of electron gas degeneracy are shown. The most probable mechanism of the sample purification due to the formation of electrically neutral complexes based on ytterbium ions and background impurities of donor and acceptor types is discussed.

Effect of ion irradiation on the structure and luminescence characteristics of porous silicon impregnated with tungsten-telluride glass doped by Er and Yb impurities

Using transmission electron microscopy and elemental analysis, it has been shown that tungsten telluride glass (TTG) containing erbium and ytterbium as impurities penetrates into pores of porous silicon (PS) when melted in vacuum at 500°C. It has been found that the intensity of photoluminescence (PL) of erbium at the wavelength of 1.54 μm in PS: TTG layers increases by a factor of up to 5 in the layers irradiated by P+ and Ar+ ions. This is assigned to ion mixing which favors interaction among the Er ions and PS-embedded Si nanocrystals initiating sensitization of the PL, as well as to broadening of the glass-impregnated PS region. Implantation of the lighter Ne+ ions affects only weakly the PL of erbium ions.

Density-functional study on the robust ferromagnetism in rare-earth element Yb-doped SnO2

So far, little has been known about the ferromagnetism induced by p–f hybridization. We investigate the magnetic properties of Yb-doped SnO2 by first-principles calculations. We find that the doped system favors the ferromagnetic state and a room-temperature ferromagnetism can be expected in it. The origin of ferromagnetism can be attributed to the p–f hybridization between Yb impurity and its surrounding oxygen atoms. The formation energy of defect complex is calculated and the magnetic mediation of intrinsic vacancies is studied. Our results reveal that the formation energy of the defect complex with Sn vacancy is about 7.3eV lower in energy than that with oxygen vacancy. This means Sn vacancy is much easier to form than oxygen vacancy in the presence of Yb substitution. The ferromagnetism of the doped system is greatly enhanced in the presence of Sn vacancies.

Reactor production and electrochemical purification of 169Er: A potential step forward for its utilization in in vivo therapeutic applications

The aim of the present study was to develop and demonstrate a viable method for the reactor production of (169)Er with acceptable specific activity using moderate flux reactor and its purification from (169)Yb following electrochemical pathway based on mercury-pool cathode to avail (169)Er in radionuclidically pure form essential for its therapeutic use. Erbium-169 was produced in reactor by neutron bombardment of isotopically enriched (98.2% in (168)Er) erbium target at a thermal neutron flux of ~8×10(13) n.cm(-2).s(-1) for 21 d. A thorough optimization of irradiation parameters including neutron flux, irradiation time and target cooling time was carried out. The influence of different experimental parameters for the quantitative removal (169)Yb from (169)Er was investigated, optimized and based on the results; a two-cycle electrochemical separation procedure was adopted. The suitablility of purified (169)Er for application in radiation synovectomy and bone pain palliation was ascertained by carrying out radiolabeling studies with hydroxypaptite (HA) particles and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminomethylene phosphonic acid (DOTMP), respectively. Thermal neutron irradiation of 10mg of isotopically enriched (98.2% in (168)Er) erbium target at a flux of ~8×10(13) n.cm(-2).s(-1) for 21 d followed by a two-step electrochemical separation of (169)Yb impurity yielded ~3.7GBq (100mCi) of (169)Er with a specific activity of ~370MBq/mg (10mCi/mg) and radionuclidic purity of >99.99%. The reliability of this approach was amply demonstrated by performing several production batches, where the performance of each batch remained consistent. The utility of the purified (169)Er was demonstrated in the radiolabeling studies with HA particles and DOTMP, wherein both the radiolabeled products were obtained with high radiolabeling yield (>99%). A viable strategy for the batch production and purification of (169)Er, suitable for therapeutic applications, has been developed and demonstrated.

Electronic structure andf-orbital occupancy in Yb-substituted CeCoIn5

The local structure and 4$f$ orbital occupancy have been investigated in Ce${}_{1\ensuremath{-}x}$Yb${}_{x}$CoIn${}_{5}$ via Yb ${L}_{\mathrm{III}}$-edge extended x-ray absorption fine structure (EXAFS), Ce and Yb ${L}_{\mathrm{III}}$-edge x-ray absorption near-edge structure (XANES), and angle-resolved photoemission spectroscopy (ARPES) measurements. Yb(III) (4${f}^{13}$) is the hole analog of Ce(III) (4${f}^{1}$). Yb is found to be strongly intermediate-valent in Ce${}_{1\ensuremath{-}x}$Yb${}_{x}$CoIn${}_{5}$ throughout the entire doping range, including pure YbCoIn${}_{5}$, with an $f$-hole occupancy for Yb of ${n}_{f}\ensuremath{\simeq}0.3$ (i.e., Yb${}^{2.3+}$), independent of Yb concentration and independent of temperature down to $T=20$ K. In contrast, the $f$-electron orbital occupancy for Ce remains close to 1 for all Yb concentrations, suggesting that there is no mutual influence on ${n}_{f}$ between neighboring Ce and Yb sites. Likewise, ARPES measurements at 12 K have found that the electronic structure along $\ensuremath{\Gamma}\ensuremath{-}X$ is not sensitive to the Yb substitution, suggesting that the Kondo hybridization of Ce $f$ electrons with the conduction band is not affected by the presence of Yb impurities in the lattice. The emerging picture is that in Ce${}_{1\ensuremath{-}x}$Yb${}_{x}$CoIn${}_{5}$ there are two networks, interlaced but independent, that couple to the conduction band: one network of Ce ions in the heavy-fermion limit, and one network of Yb ions in the strongly intermediate-valent limit. The robustness of the local and electronic structure to doping suggests the absence of charge transfer between the Ce and Yb ions, and may explain the relative robustness of superconductivity for this Ce-site substitution as compared to the In-site substitution.

Electronic spectra of Yb2+-doped SrCl2

The absorption and emission spectra of Yb(2+)-doped SrCl(2) have been calculated on the basis of ab initio quantum chemical calculations which consider recently found, unexpected excited states with double-well energy curves and complex electronic structure, resulting from avoided crossings between Yb-trapped excitons and Yb impurity states, which influence prominent spectral features. The root mean square deviation and largest absolute error of the calculated energy levels are 394 and -826 cm(-1), respectively. The YbCl(8) moiety breathing mode vibrational frequencies and bond lengths of the lowest states are consistent with observed vibrational progressions and energy shifts induced by uniaxial compression. Photoionization is predicted above 49,000 cm(-1) as a consequence of the spin-orbit induced spreading of the Yb-trapped exciton character in the upper part of the spectrum and three new emission bands are predicted with origins at about 33,800, 36,400, and 43,600 cm(-1). The electron correlation methods used overestimate the relative stabilization of the 4f(14) ground state and this leads to a constant error of the whole absorption spectrum of about 3500 cm(-1) (23%-7%). Although this energy shift is customarily considered an adjustable parameter, it is a nonparametric, direct product in an ab initio route which shows the limitations on the proper representation of differential correlation between the 4f(N) and 4f(N-1)5d (or similar) configurations and the need for theoretical improvement.

Detection of Yb impurities in the VUV spectral range of NdGaO 3 crystals

Substantial influence of the 1 at.% Yb doping of NdGaO 3 single crystals on the optical functions ε 1( E) and ε 2( E) in the spectral range of electronic excitations is established. The corresponding differences of the optical functions for pure and doped NdGaO 3 have been monitored using spectroscopic ellipsometry method and synchrotron radiation light source. This opens an opportunity for the spectroscopic diagnostics of the rare earth dopants in crystals using the spectroscopic information concerning the electronic inter-band optical transitions. To understand better the experimental results obtained, the ab-initio calculations of band structure and optical spectra of the centrosymmetric single crystal NdGaO 3 have been performed using the VASP code (Vienna Ab-initio Simulation Package). The calculated dielectric functions ε 1( E) and ε 2( E) agree satisfactorily with our experimental results obtained with using the spectroscopic ellipsometry method and synchrotron radiation. It was demonstrated that differences of the optical functions for pure and doped crystals using stable synchrotron source may serve as a powerful tool for spectroscopic diagnostic of localised rare earth ions with respect to the strong inter-band transitions.

Temperature dependence of the principal and additional refractive indices of Yb:KGW and KYW crystals in the range of 20–400°C

The temperature dependence of the principal refractive indices of potassium-gadolinium tungstate crystals with 7% Yb impurity and pure potassium-yttrium tungstate without impurities has been measured for seven wavelengths in the visible spectral range at temperatures of 20–400°C. It is shown that the thermooptical coefficients for each crystal have different signs at a fixed wavelength. Based on measurements of the temperature behavior of the principal and additional refractive indices and analysis of their thermooptical coefficients, some athermal directions are found in both crystals.

Effects of Yb impurity on Er‐related emission in Al0.70Ga0.30As:Er,Yb epitaxially grown on GaAs substrate

AbstractThe effects of Yb impurity on the optical properties of an Er,Yb‐implanted Al0.70Ga0.30As epitaxial layer were studied. The defect characterizations were carried out for undoped Al0.70Ga0.30As and Al0.70Ga0.30As:Er,Yb samples annealed in the temperature range from 500 °C to 900 °C. From results of photoluminescence (PL), Raman spectroscopy and positron annihilation spectroscopy, it was found that the implantation damage in Al0.70Ga0.30As:Er,Yb samples are recovered by the thermal annealing at a temperature above 700 °C. Maximum PL intensity of Er‐related emission was observed from the Al0.70Ga0.30As:Er,Yb sample annealed at 800 °C. The energy transfere from Yb3+ to Er3+ was also investigated by selectively excited photoluminescence (PL) and PL excitation spectroscopy. It was also observed that the energy was transfered from Yb3+ to Er3+. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation and characterization of n- and p-type ytterbium doped InP epitaxial layers

In this paper we pursue the effect of ytterbium (Yb) addition on the physical properties of liquid phase epitaxially (LPE) grown thin InP layers. A series of InP layer samples were prepared by LPE from melts containing 0–0.4 wt% of Yb. The grown layers were examined by Hall effect and C-V measurements, photoluminescence (PL) spectroscopy, and Rutherford backscattering spectrometry (RBS). We have found that Yb impurity was incorporated into the lattice of InP layer. With increasing Yb content in the growth melt the layer’s conductivity smoothly changed from n- to p-type when the Yb admixture exceeded a certain limit. On the basis of these results we prepared p-n junctions in the InP layers directly doped by Yb, and tested them by C-V measurements.

Preparation and properties of Er and Yb doped InP-based semiconductor compounds

In this paper we pursue the effect of the erbium and ytterium addition during the liquid phase epitaxial (LPE) growth on physical properties of thin InP layers. Series of InP layer samples were prepared by LPE from the melts containing 0–0.3 wt.% of Er and Yb. The grown layers were examined by the Hall effect andC-V measurements, photoluminescence spectroscopy and Rutherford backscattering spectrometry (RBS). We have found that only Yb impurity was incorporated into the lattice of InP layer. With increasing Yb content in the growth melt the layer’s conductivity smoothly changed from n to p type when Yb admixture exceeded certain limit. On the basis of these results we prepared p-n junctions in the InP layers directly doped by Yb, and tested then byC-V measurements.

A-centers modifying in CdTeYb crystals

By means of electrical and magnetic investigation of Yb-doped CdTe crystals, the following was established: (1) Additional shallow donors and paramagnetic centers are not introduced into the doping process; the hole conductivity of doped crystals is controlled by A-centers; their ionization energy depends on Yb impurity concentration (C) according to the law E A = (0.15 + 2.4 × 10 −11 C −1 2 ) eV; (2) It is supposed that Yb impurity deforms the lattice so that the components of the complex A-center move away one from another when the concentration ( C) increases; and E A increases accordingly.